26-04-2025
New 4D quantum sensors may help physicists trace the birth of space and time
Smashing subatomic particles together at near-light speeds has long been the best way to understand the universe's fundamental building blocks.
These high-energy collisions, conducted inside massive particle accelerators, help physicists study matter, energy, space, and time.
As new accelerators promise even more powerful and chaotic collisions, scientists need tools far more advanced than those used before.
That's where quantum sensors come in.
A team from Fermilab, Caltech, NASA's Jet Propulsion Laboratory (JPL), and several international institutions has developed a new type of detector that could redefine how we study particle collisions.
These superconducting microwire single-photon detectors, or SMSPDs, were recently tested at Fermilab and showed exceptional precision in detecting particles produced during high-energy beams.
As future colliders reach greater energies and particle intensities, physicists expect to encounter a flood of data — sprays of particles flying out in all directions.
That makes detection more complex than ever.
According to Maria Spiropulu, the Shang-Yi Ch'en Professor of Physics at Caltech, 'In the next 20 to 30 years, we will see a paradigm shift in particle colliders as they become more powerful in energy and intensity.
And that means we need more precise detectors.'
SMSPDs offer a breakthrough by detecting both time and spatial information at once, something traditional detectors can't do.
Fermilab scientist Si Xie, who also holds a joint appointment at Caltech, explains that these are essentially '4D sensors' because they combine spatial and time resolution, eliminating the need to compromise between the two.
In their first major test, the SMSPDs were exposed to high-energy beams of protons, electrons, and pions at Fermilab.
The detectors outperformed conventional systems in both time precision and spatial tracking.
Determining exactly when and where particles travel is crucial when analyzing the millions of interactions that happen each second in particle collisions.
'The novelty of this study is that we proved the sensors can efficiently detect charged particles,' says Xie.
Unlike their predecessors, superconducting nanowire single-photon detectors (SNSPDs), which are better suited for quantum networking or space-based optical communication, SMSPDs have a larger surface area and are capable of tracking particles that are key to high-energy physics experiments.
The detectors could make it possible to identify lower-mass particles or entirely new ones, such as those hypothesized to make up dark matter.
Xie sees this as just the beginning: 'We have the potential to detect particles lower in mass than we could before as well as exotic particles like those that may constitute dark matter.'
Precision is vital in identifying such elusive targets.
As Spiropulu puts it, 'Back in the 1980s, we thought having the spatial coordinates were enough, but now... we also need to track time.'
The SMSPDs help researchers trace particles in four dimensions, offering an edge in navigating the overwhelming complexity of modern collider environments.
These quantum detectors may become foundational to future colliders, including the proposed Future Circular Collider or a muon collider.
Fermilab scientist Cristián Peña, who led the research, sees the technology as a timely advancement.
'We are very excited to work on cutting-edge detector R&D like SMSPDs because they may play a vital role in capstone projects in the field,' he says.
